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  • Haemophilus Influenzae
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  • 1
    Language: English
    In: PloS one, 2015, Vol.10(4), pp.e0124373
    Description: Haemophilus ducreyi resists the cytotoxic effects of human antimicrobial peptides (APs), including α-defensins, β-defensins, and the cathelicidin LL-37. Resistance to LL-37, mediated by the sensitive to antimicrobial peptide (Sap) transporter, is required for H. ducreyi virulence in humans. Cationic APs are attracted to the negatively charged bacterial cell surface. In other gram-negative bacteria, modification of lipopolysaccharide or lipooligosaccharide (LOS) by the addition of positively charged moieties, such as phosphoethanolamine (PEA), confers AP resistance by means of electrostatic repulsion. H. ducreyi LOS has PEA modifications at two sites, and we identified three genes (lptA, ptdA, and ptdB) in H. ducreyi with homology to a family of bacterial PEA transferases. We generated non-polar, unmarked mutants with deletions in one, two, or all three putative PEA transferase genes. The triple mutant was significantly more susceptible to both α- and β-defensins; complementation of all three genes restored parental levels of AP resistance. Deletion of all three PEA transferase genes also resulted in a significant increase in the negativity of the mutant cell surface. Mass spectrometric analysis revealed that LptA was required for PEA modification of lipid A; PtdA and PtdB did not affect PEA modification of LOS. In human inoculation experiments, the triple mutant was as virulent as its parent strain. While this is the first identified mechanism of resistance to α-defensins in H. ducreyi, our in vivo data suggest that resistance to cathelicidin LL-37 may be more important than defensin resistance to H. ducreyi pathogenesis.
    Keywords: Bacterial Proteins -- Genetics ; Drug Resistance, Bacterial -- Genetics ; Ethanolaminephosphotransferase -- Genetics ; Haemophilus Ducreyi -- Genetics ; Lipid A -- Metabolism
    E-ISSN: 1932-6203
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  • 2
    Language: English
    In: Infection and immunity, 04 January 2016, Vol.84(3), pp.765-74
    Description: Haemophilus haemolyticus and nontypeable Haemophilus influenzae (NTHi) are closely related upper airway commensal bacteria that are difficult to distinguish phenotypically. NTHi causes upper and lower airway tract infections in individuals with compromised airways, while H. haemolyticus rarely causes such infections. The lipooligosaccharide (LOS) is an outer membrane component of both species and plays a role in NTHi pathogenesis. In this study, comparative analyses of the LOS structures and corresponding biosynthesis genes were performed. Mass spectrometric and immunochemical analyses showed that NTHi LOS contained terminal sialic acid more frequently and to a higher extent than H. haemolyticus LOS did. Genomic analyses of 10 strains demonstrated that H. haemolyticus lacked the sialyltransferase genes lic3A and lic3B (9/10) and siaA (10/10), but all strains contained the sialic acid uptake genes siaP and siaT (10/10). However, isothermal titration calorimetry analyses of SiaP from two H. haemolyticus strains showed a 3.4- to 7.3-fold lower affinity for sialic acid compared to that of NTHi SiaP. Additionally, mass spectrometric and immunochemical analyses showed that the LOS from H. haemolyticus contained phosphorylcholine (ChoP) less frequently than the LOS from NTHi strains. These differences observed in the levels of sialic acid and ChoP incorporation in the LOS structures from H. haemolyticus and NTHi may explain some of the differences in their propensities to cause disease.
    Keywords: Haemophilus -- Metabolism ; Haemophilus Infections -- Microbiology ; Haemophilus Influenzae -- Metabolism ; Lipopolysaccharides -- Chemistry ; N-Acetylneuraminic Acid -- Analysis ; Phosphorylcholine -- Analysis
    ISSN: 00199567
    E-ISSN: 1098-5522
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  • 3
    Language: English
    In: Biomedical & Environmental Mass Spectrometry, November 1990, Vol.19(11), pp.731-745
    Description: A structural model is proposed for the surface glycolipids, or lipooligosaccharides (LOS), of gram‐negative pathogenic bacteria that colonize human mucosae, e.g. and The development of this model has involved analysis of a series of pyocin‐resistant mutants with altered LOS and other recent immunochemical and structural data. A comprehensive approach to determining the necessary structural data has been constructed that utilizes liquid secondary ion mass spectrometry, tandem mass spectrometry, methylation analysis and nuclear magnetic resonance. To prepare purified oligosaccharides for these analyses, chromatographic and chemical techniques have been developed that include high‐pH anion‐exchange chromatography of underivatized oligosaccharides and reverse‐phase chromatography after derivatization with hydrazino alkyl benzoates. The proposed LOS model has several unique features that distinguish it from models developed for the lipopolysaccharides of enteric bacteria. This information should lead to an understanding of the unique structure/function relationship of LOS and to the development of carbohydrate‐based vaccines.
    Keywords: Bakterien ; Krankheitserreger ; Lipoprotein ; Strukturanalyse ; Oberflaechenstruktur ; Immunozytochemie ; Massenspektrometrie ; Kernresonanzspektrometrie ; Ionenaustauschchromatographie ; Zellmembran ; Theoretisches Modell ; Oligosaccharid ; Biology ; Anatomy & Physiology;
    ISSN: 0887-6134
    E-ISSN: 1096-9888
    E-ISSN: 23763868
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